State Department officials would not specify whether a batch of Hillary Clinton's private emails slated for release Saturday would contain more "top secret" documents.

"I don't have any preview to offer you or details about what this batch may hold," Mark Toner, an agency spokesman, told reporters Friday. "We've been very clear all along in this process as we review these emails, we'll upgrade them as is seen necessary. And we'll continue to do that. But I don't have anything to preview, sorry."

When the State Department published 1,118 pages of Clinton's emails at the end of January, it withheld 37 pages that contained top secret information. More than 1,600 emails have been upgraded to some level of classification since the agency began releasing them in May of last year.

Earlier this week, a federal judge ordered the State Department to publish as many emails as possible in four separate installments spread across the month of February. The court order rejected the agency's request that it be allowed to wait until the end of the month to publish the remaining Clinton emails.

"Obviously it's tomorrow, and so we're still working diligently on this," Toner said of the Saturday email release, which should include 550 emails.

"So we'll be able to let all or many of you know what time we expect that release to take place and then we'll also issue whatever more information or characterization we can provide at the time," he added.

Toner said he could not give an estimate of how many emails would be considered classified in the upcoming trove.

As many as 29 emails have been upgraded to "top secret" this year, and the agency could upgrade significantly more before February is over.